As the world population has been aging and trying to remain more active, there has been an increased prevalence of damage not only to bones, but also to soft tissues. Damage to soft tissue can lead to decreased mobility and increased pain. Therefore, repair and healing of soft tissue is important. Two of the types of soft tissue with respect to which repair and healing are particularly important are tendons and ligaments.
Tendons are specialized connective tissue that connect and attach muscles to bones. Tendons transmit tensile loads from muscles to the attached bones, thereby causing movement of the bones around joints. In order to accomplish their desired function, tendons must be able to sustain high tensile forces, but they also must be flexible enough to bend around bony surfaces.
Ligaments are also specialized connective soft tissues. They connect and attach bones to other bones. Ligaments provide stability to joints by being flexible enough to allow natural movement of the bones, yet also by being strong and inextendible, thereby preventing resistance to applied forces. Thus, in order for bones and muscles to function properly, tendons and ligaments need to be able to function properly as well.
In both tendons and ligaments, bundles of collagen fibers are embedded in a connecting matrix that may be referred to as a ground substance. The collagen usually consists mainly of Type I collagen fibers. These bundles of collagen fibers provide the load carrying elements, and they are aligned to resist the applied tensile loads. In tendons, the collagen fibers are arranged in nearly parallel formation, thereby enabling them to withstand high unidirectional loads. In ligaments, the collagen fibers are arranged in a less parallel formation, thereby enabling them to withstand predominant tensile stresses in one direction and smaller stresses in other directions. Both tendons and ligaments contain cells in low density occurrence in relation to the extracellular matrix in which they reside. Unfortunately, this low density provides them with a limited capacity for healing when injured. Small tears can heal by themselves, but larger tears require surgical intervention in the form of suturing, and in the case of tendons, complete breaks often require replacement of the tendon itself.
Additionally, very often the healing process results in the formation of scar tissue, which consists of non-aligned fibers. Typically scar tissue forms with a large type III collagen component, and it is much weaker than the original tissue.
Given the importance of tendons and ligaments, there is concern that when they tear or deteriorate, persons with the damaged tissue will suffer decreased mobility and increased pain. The present application provides compositions and methods that may be used to assist in the repair or healing of these tissues.